Lichenomphalia chromacea (Yellow Navel)

In Lichenomphalia chromacea the fruit body produced by the fungal partner in the lichen is a mushroom that appears on soil. It is yellow throughout, with a smooth, dry cap up to about 2 centimetres across and with a central depression.  The stems may be up to about 2 centimetres long and the gills run down the stem a little. In this lichen the fruit body is the dominant feature and the associated algal cells appear as a green mat  on the soil surface. That mat need be nothing more than a sparse green wash on the soil.

A number of non-lichenized fungi produce similar types of fruit bodies (see Omphalina s.l.: http://canberranaturemap.org/Community/Species/20395).  To be sure that you have Lichenomphalia chromacea check both that the colour is yellow and that there is a green, algal mat on what is otherwise bare soil around the yellow mushrooms.   

The other species of Lichenomphalia known from the local region is the brown Lichenomphalia umbellifera (https://admin-canberra.naturemapr.org/Community/Species/Sightings/45284).